1. Field of the Invention
This invention relates to cannulas of the type used to perform laparoscopic surgery and, more particularly, to structure for maintaining a cannula in operative position with respect to body tissue through which the cannula extends.
2. Background Art
In performing laparoscopic surgery, an incision is made in a patient to admit a cannula which serves as a conduit for the introduction of selected surgical instruments into a body cavity. During a surgical procedure, several cannulas may be directed into the patient at spaced locations to facilitate simultaneous use of a number of instruments. The body cavity in which the operation is performed is filled with a gas to expand the surrounding tissue to create a suitably sized operating space.
In designing laparoscopic equipment, there are several objectives. First, it is important to confine the gas used to expand the cavity in which the operation is to be performed with the cannula in operative position. Deflation of the body cavity could result in interruption of a surgical procedure and/or injury to the patient's internal organs.
It is also important that the cannula be positively maintained in its operative position on the body tissue through which it passes. By positively positioning the cannulas, internal and external clashing between multiple instruments is minimized.
A further objective is to permit the cannula, in its operative position, to be reoriented with respect to a cavity to maximize the working range for each instrument and thereby minimize the number of cannulas that must be used.
Generally, the above three objectives are competing. For example, by positively maintaining the cannula in its operative position, the leakage of gas may be minimized, however the range of motion for the instrument extending through the cannula may be limited.
Examples of prior art structures utilized to maintain a cannula in an operating position with respect to tissue through which the cannula extends are shown in each of U.S. Pat. Nos. 3,039,468, to Price; 3,253,594, to Matthews et al; 3,459,175, to Miller; and 4,077,412, to Moossun. In each of the above four patents, a disk with a large surface area is borne against one side of a tissue through which the cannula extends to thereby positively maintain the position of the cannula. The large contact area between the disks and tissue minimizes the amount of permissible repositioning of the cannula with respect to the tissue. Further, if the disk is brought sufficiently tightly against the tissue to maintain the position of the cannula, the underlying tissue may be traumatized.
There is another drawback with prior art structures utilizing an inflatable balloon/membrane to maintain the cannula in operative position. With such devices, a balloon is inflated to provide an obstruction to removal of the cannula from an incision. A tube/conduit is required to selectively inflate and deflate the balloon from a point externally of the body.
Exemplary prior art conduits are shown in U.S. Pat. Nos. 3,253,594, to Matthews et al and 3,459,175, to Miller. In each, the exposed conduit is separately passed through an incision in the body tissue. The opening for the conduits affords another escape route for gas within the cavity. The conduits are also prone to being severed or pinched. Further, the conduits are difficult to clean and potentially unsanitary when reused.
The present invention is specifically directed to overcoming the above-enumerated problems in a novel and simple manner.